Drivers of spatial and temporal variability in estuarine food webs

A critical challenge to understanding the response of ecosystems to anthropogenic drivers is characterizing the spatial and temporal variability of controls on food web dynamics. We used a long-term (9 yr) isotope survey and a community metric isotope approach to determine the major physical factors influencing the source of energy to estuarine food webs. Overall, food web architecture was similar throughout the estuary, but there were some spatial differences. We observed greater overall variability in the primary production source to the food web in the upper estuary (which is more influenced by freshwater inputs) compared with the middle and lower estuary. The trophic level of one dominant species, mummichog Fundulus heteroclitus, was also highly correlated with tidal height, which controls high marsh access in the middle estuary. We also observed a strong influence of freshwater input on the benthic-pelagic coupling in the upper estuary. Our work demonstrates that the temporal and spatial variability of food webs in estuarine systems is highly coupled to physical drivers.